Lagers ferment at a much lower temp than ales. I think the norm is ~55F. It's my understanding that the fermentation takes closter to a month, and the beer needs to stay at constant temperature.

I personally have no way to get the temp that low and keep it close to constant, so I brewed my Oct-fest as an ale. I'm sure some of the other guys will have some suggestions on getting it to the right temp, though.

Typically, lagers are fermented from 45-55F and then conditioned at a lower temp, 32-45F for 2 or 3 months (or longer in some cases).

If you don't have a dedicated fermentation fridge, I'd just stick the bottles in your normal fridge and let 'em cold condition for a month after they've had a chance to carbonate. If that's not an option, get it as cool as you can within your limitations.

If you're unsure of the lager yeast's vitality, I'd let the batch naturally carbonate for a week or two at the upper end of the lager range (let's say 55-60F) to make sure it happened, and then drop the temperature and lager until served.

If you're not worried about yeast vitality, there's no reason you can't naturally carbonate with temps in the 40s. The process would just take longer. But if you don't plan on touching it for a month or two, it wouldn't be a big deal.

As far as kegging, after my secondary period I dump the batch into kegs and let it age near freezing, 32-35F, while I force carbonate it, then I wait as long as I can before I tap it

If you plan on aging your beer for any length of time around 40F there is a real good chance that your yeast will drop out of suspension and will not be viable to ferment your priming sugar or malt for carbonation. Most liquid lager strains will only be effective between 48 and 58 degrees. To be on the safe side I would not drop the temperature below 50 until after carbonation takes place, unless you plan to force carbonate. After carbonation the beer can be cooled to as cold as you like for lagering.